The Organic Light Emitting Display (OLED) possesses many outstanding properties of self-illumination, low driving voltage, high luminescence efficiency, short response time, high clarity and contrast, near 180° view angle, wide range of working temperature, applicability of flexible display and large scale full color display. The OLED is considered as the most potential display device.
The OLED can be categorized into two major types according to the driving methods, which are the Passive Matrix OLED (PMOLED) and the Active Matrix OLED (AMOLED), i.e. two types of the direct addressing and the Thin Film Transistor (TFT) matrix addressing. The AMOLED display comprises pixels arranged in array and belongs to active display type, which has high lighting efficiency and is generally utilized for the large scale display devices of high resolution.
AMOLED display is driven with electrical current, and the pixel structure generally comprises two transistors, a storage capacitor and an organic light emitting diode. The organic light emitting diode is a current driving element. When the electrical current flows through the organic light emitting diode, the organic light emitting diode emits light, and the brightnesses thereof various levels are generated according to the different currents flowing through.
The organic light emitting diode generally comprises an anode, a Hole Injection Layer, a Hole Transporting Layer, an emitting material layer, an Electron Transport Layer, an Electron Injection Layer and a cathode. The higher the display brightness of the organic light emitting diode, the decay of materials of the respective layers inside is more serious. Therefore, to reduce the display brightness of the image of the AMOLED display can extend the lifetime of the AMOLED display. As shown in FIG. 1, the method of extending lifetime of the AMOLED display according to prior art is to reduce the entire brightness of the display image. In FIG. 1, the straight line y10 represents the original display brightness of the image shown by the AMOLED display, and the straight line y20 represents the display brightness after the brightness of the image shown by the AMOLED display is reduced. Such operation can extend the lifetime of the AMOLED display, but the entire brightness is reduced, and the display effect of the AMOLED display is influenced.